Booster device

ABSTRACT

A device useful in explosives technology comprising a high explosive composition of matter shaped so that there is provided within said composition at least one aperture, the combination thereof with at least one flexible resilient restraining member situated within said composition in such a manner that at least a part of said member lies within or protrudes into said aperture. Methods of preparing and using such a device are also described.

United States Patent Huggins et al. Dec. 3, 1974 BOOSTER DEVICE 3,212,438 l0/l965 Lawrence 102/24 R 3,311,056 3 1967 N dd' I02 27 R [75] Inventors: Arthur Huggins, Essendon; Darrell 0 m Andrew Williams, West Heidelberg, Vlctona, both of Austraha Primary Examiner--Stephen J. Lechert, Jr. 731 Assignee: ICI Australia Limited, Melbourne, Attorney, Agent, or Firmcushman, Darby &

Victoria, Australia Cushman [22] Filed: Feb. 26, 1973 [21] Appl. No.: 336,076

[57] ABSTRACT [30] Foreign Application Priority Data A device useful in explosives technology comprising a Mar. 8, 1972 Australia 8205/72 high explosive composition of matter shaped SO that there is provided within said composition at least one 102/24 102/27 aperture, the combination thereof with at least one 264/3 R flexible resilient restraining member situated within [51] hit. Cl. C06C 11/00 said composition in such a manner that at least a part Field Of Search 102/24 27 of said member lies within or protrudes into said aper- 264/3 R ture. Methods of preparing and using such a device are also described. [56] References Cited UNITED STATES PATENTS 6 Claims, N0 Drawings 3,037,452 6/!962 Cook et al. 102/27 R BOOSTER DEVICE This invention relates to devices commonly referred to in the explosives industry as boosters.

In the explosives industry explosives are used for many purposes one of which is their use as a blasting medium. It is common practice to load a borehole drilled into an ore body with a main explosive charge of a blasting composition and to detonate this main explosive charge by means of a detonator or a booster. A booster is defined as a device comprising a sensitive secondary high explosive composition of matter which on detonation reinforces the detonation wave from a primary explosive or a detonating means. Such a device delivers thereby a more powerful detonation wave to the main explosive charge.

Boosters are well known and usually comprise a shaped, sensitive high explosive composition located within a casing, typically a paper, cardboard or plastic, for example high density polyethylene, container. The nature of the high explosive composition is not narrowly critical provided such a composition is sensitive to detonation by commercial means for example by means of detonating fuse or detonators. From amongst typical compositions used in boosters there may be mentioned those of the so-called pentolite type comprising a mixture of trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN). Other booster compositions which may be used include compositions comprising TNT and trinitrotrimethylenetriamine (RDX), for example the well known Composition B which contains about 60 percent w/w RDX, about 39 percent w/w TNT and about 1 percent w/w wax.

The size and shape of the composition in boosters vary with the use to which the device is to be put; thus typical boosters vary in weight from 1 ounce to 1 pound or even more. Although boosters of an irregular shape may be used for certain purposes it is preferred that they be of a regular design for example in the form of a cylinder. Typical overall dimensions of such a cylindrical configuration are a diameter in the range from 0.5 to 3 inches and a length in the range from 1 to 8 inches. A very suitable cylindrical configuration is one in which the ratio of length to diameter is in the range from 3:1 to 1:1, for example 2:1.

The composition maybe loaded or cast into a casing in the form of a solid block. Alternatively the volume and shape of the cast composition may be chosen such that the volume of the casing is not occupied fully by the block. In another and more usual arrangement the cast composition is so shaped that its overall dimensions are such that it fits snugly within the casing, but the composition has one or more apertures leading from its exterior to the interior portion of the booster composition. The aperture or apertures in this last arrangement may be located within the composition at any convenient position. Thus such an aperture or apertures may be situated so as to be substantially parallel to a major axis of the composition; alternatively they may be inclined at an angle to such an axis. For example in the instance where the composition is in the form of a regular right cylinder, the major dimension of the aperture may run parallel or substantially parallel to the length of the cylinder; alternatively it may run parallel or substantially parallel to the diameter of the cylinder; yet again it may run at an angle in relation to the length and diameter of the cylinder. Such an aperture or apertures may be located in the composition at regular or irregular positions. Thus for example when the composition is cast so that it has only one aperture in its shape, such an aperture could be positioned so that it is located centrally within the composition. Alternatively where two or more apertures are present they may be located so as to form a regular pattern. Yet again such an aperture could be placed non-centrally or a series of apertures could be located in an irregular pattern, say all towards one edge of the composition or with a certain number towards one edge and with a different number towards the centre or an opposite edge. A very convenient location for a single aperture in a composition which is shaped as a regular right cylinder is one where the aperture is located centrally or approximately centrally within the composition and the longest dimension of the aperture is parallel or approximately parallel to the height of the cylinder.

The apertures may be of any convenient shape; a very convenient shape is an aperture in the form of a hollow right cylinder. Thus for example in a composition in the shape of a regular right cylinder of length 1.25 inches and of diameter 1 inch a convenient aperture is a hole extending throughout the length of the cylinder, situated centrally therein and of fivesixteenths inch diameter. For boosters of greater size, say of length of from 2 to 3.5 inches and of diameter of from 1.5 to 3 inches it is convenient to have as apertures two or more holes of a minimum diameter of 0.25 inches spaced at 1 inch centres around the central axis. Whilst for some applications it is convenient to use apertures which extend throughout the booster composition so that they are open at both ends, it is sometimes convenient for other applications to use apertures which terminate within the body of the composition, that is to say such apertures are open at one end only. For certain further applications the bore or diameter of the apertures may be varied so that a constriction within the aperture is formed or yet again one end of the aperture may be closed in part to leave an orifice therein which is smaller than the opening at the opposite end of the aperture.

The apertures described above have been used hitherto for locating detonators or fuse: cord in close proximity to the booster composition. It has been common practice to insert an appropriate detonator or detonators in a suitably sized aperture or apertures in such booster compositions prior to placing the detonator booster combination in its desired position in a borehole. Whilst such a technique has been reasonably satisfactory hitherto it has been found that under certain conditions, for example the use of boosters in long boreholes or in boreholes which are bored upwardly in a rock or ore face the so-called upholes the detonators have not remained in their desired position in the aperture or apertures and in some instances it has been found that the detonator and the booster have become partially or completely separated during attempts to place them in a desired position in a borehole. Such occurrences have led to undesired misfires in blasting operations.

We have now found that the deficiencies of the prior art may be reduced considerably and often overcome completely if there is incorporated within the explosive composition of a booster one or more flexible restraining members situated in such a manner that such member or members encompass an aperture or apertures wherein detonating means, for example a detonator or a detonating cord, may be located so as to reduce the tendency for the booster composition and the detonating means to become separated.

Accordingly we provide in a known device comprising a sensitive secondary high explosive composition of matter capable of reinforcing a detonation wave from a primary explosive or detonating means and commonly referred to as a booster, and wherein said composition of matter is shaped so that there is provided within said composition of matter one or more apertures, the combination thereof with one or more flexible resilient restraining members situated within said composition of matter in such a manner that at least a part of said member (5) lies within or protrudes into said aperture or apertures. The flexible restraining member may be for example a flexible sleeve with which the aperture is lined or may be in the form of an annulus the larger circumference of which encompasses the aperture and the smaller circumference lies within the aperture.

The composition and dimensions of the flexible restraining member are not narrowly critical provided it is capable of being deformed and has elastic properties. Typically such a member may be made from a natural or synthetic rubber or plastic composition. In the instance where the apertures are cylindrical holes we have found that rubber rings available commercially from lrwin Hunter & Co Pty Ltd of Melbourne, Australia, under the Trade Name of Sealing Ring, or from Elastrator (Aust.) Pty Ltd of Melbourne, Australia, under the Trade Name ofElastrator," are particularly suitable.

Our improved device is of particular utility in providing a means whereby one or more detonators may be located in close proximity to an explosive composition of matter used in a booster. Thus for example a detonator may be inserted into an aperture of a booster which has been modified according to our invention. By suitable choice of the dimensions of the detonator and the restraining means, for example, a rubber ring, and by suitably positioning the restraining means a detonator may be held in a desired position by the restraining means. It will be appreciated that under certain circumstances, for example when the detonator is comparatively large, a series of individual restraining means may be required to adequately hold a single detonator in a desired position in an aperture.

Accordingly we provide a process of locating a detonating means in a desired position and in spaced relationship to an explosive composition of matter shaped so that there is provided within said composition of matter one or more apertures which process comprises firstly locating one or more flexible restraining members within said composition of matter in such a manner that at least a part of said member(s) protrudes into said aperture or apertures; secondly inserting and locating a detonating means into said aperture in a manner such that the outer surface of the detonating means comes into contact with said restraining member(s) thereby creating a frictional resistance between said detonating means and said member sufficient to reduce the tendency for the detonating means to move from said desired position. Our process is useful for locating detonating cord within a booster and is especially useful when the detonating means is in the form of detonators for example in the form of the well known types of commercial detonators such as instantaneous detonators and delay detonators.

Devices according to our invention may be prepared by methods analogous to those used in the preparation of known shaped boosters but wherein additionally one or more flexible restraining means are incorporated within the apparatus used to shape the device.

Accordingly we provide in a known process of preparing a device comprising a shaped explosive compo sition of matter which process comprises the steps of 1) preparing a molten explosive composition; (2) transferring said molten composition to a mould or casing fitted with at least one former suitable for producing an aperture in said composition; and (3) cooling said composition so as to produce a shaped explosive composition of matter, the combination thereof with the additional step of locating on said former or formers one or more flexible restraining members prior to transferring said molten composition to said mould.

Our invention is useful in the realms of explosive technology in general and in particular where blasting is required during mining operations. The frequency of failures using devices according to our invention during blasting is reduced considerably when compared with the rate of failure using prior art devices, particularly where explosive compositions are to be detonated in upholes.

Accordingly we provide in a known method of blasting wherein a device comprising a sensitive secondary high explosive composition of matter is used to reinforce the detonation wave from a detonating means thereby delivering a more powerful detonation wave to a main explosive charge the improvement wherein the detonation wave is reinforced by the use of a device according to our invention.

Our invention is now illustrated by, but is in no way restricted to, the following examples wherein all parts and percentages are expressed on a weight basis.

EXAMPLE 1 Equal quantities by weight of trinitrotoluene and pentaerythritol tetranitrate were mixed in a heated jacketed vessel to form a molten mixture. A cylindrical cardboard container of diameter 1 inch and length 1.25 inches open at one end was placed by means of a threeeighths inch diameter orifice in the closed end of the container over a cylindrical brass water cooled former. The former had an external diameter of five-sixteenths inch and extended from the centre of the circular base of the container in a direction substantially parallel to the length of the container for a distance of 1.5 inches. A thick walled circular rubber ring, commercially available under the Trade Name of Scaling Ring, which had an overall diameter of 0.5 inch and a diameter between the interior surfaces of the wall of threesixteeenths inch was placed on the former in a position such that it was positioned centrally within the container. The molten mixture described above was poured into the container prepared as described above and the mixture was allowed to cool until it became solid. The solidified mixture with the container was separated from the former. There was thus obtained in the container an explosive composition shaped so that a cylindrical aperture of diameter five-sixteenths inch extended from top to bottom of the composition and wherein there was situated a flexible rubber ring and wherein a first part of the walls of the said ring were embedded in the composition and a second part of the walls of the said ring protruded into the aperture and remained in a flexible and compressable state. The device so obtained was suitable for use as a booster in blasting operations.

EXAMPLE 2 The general procedure of Example 1 was repeated but the cardboard container of that Example was replaced by a cylindrical container formed from high density polyethylene and having a diameter of 1 inch and a length of 8 inches. The number of rubber rings used was increased to two and these were located in the aperture and the matrix of the composition so that one of the rings was situated 2 inches from one end of the aperture whilst the other ring was situated 2 inches from the opposite end of the aperture. A booster suitable for use with explosives was thus obtained.

EXAMPLE 3 EXAMPLE 4 The general procedure of Example 1 was repeated but the rubber ring used in that Example was replaced by a hollow thickwalled rubber cylinder which was 1 inch long and had an internal diameter of threesixteenths inch. The rubber cylinder was located on the former in a position that it lay equidistant from either end of the former. There was thus obtained an apertured booster wherein the aperture was lined internally in part with a rubber sleeve.

EXAMPLE 5 The general procedure of Example 4 was repeated but the rubber cylinder of that Example was replaced by a similar cylinder fabricated from a flexible resilient foamed polyurethane composition. There was thus obtained a booster suitable for use with explosives.

EXAMPLE 6 A detonator having an external diameter of 0.25 inch was inserted into the aperture and ring of the device described in Example 1 until the detonator was gripped firmly by the ring around its circumference. The apparatus so formed comprising the device and the attached detonator were then used to detonate a charge of an explosive slurry composition located in a borehole which had been drilled vertically upwards into the face of an ore body.

EXAMPLE 7 The general procedure of Example 1 was repeated except that in the present Example an alternative form of apparatus was used to shape the aperture. The cylin drical cardboard container used in the present Example had a diameter of 1 inch and a length of 1.25 inches and was open at one end as in Example 1, but the orifice in the closed end was reduced in diameter to oneeighth inch. The container was placed over a brass pin which was set in a wooden block and protruded through the orifice in the container for a distance of 2 inches coaxially with the length axis of the container. A rubber ring as described in Example 1 was positioned on the exterior of a 2 inch length of semirigid nylon tubing of nine thirty-seconds inch outside diameter such that the ring was one-half inch from one end of the nylon tube. The nylon tube was then placed over the brass pin so that the nylon tube was substantially coaxial with the pin and was in contact with the end of the container in which the orifice was present and the rubber ring was positioned within the body of the container. There was thus obtained a booster similar to that described in Example 1 except that in the present Example the openings at the extremities of the aperture were of differing diameter.

We claim:

1. In a known device comprising a sensitive secondary high explosive composition of matter capable of reinforcing a detonation wave from a primary explosive or detonating means and commonly referred to as a booster, and wherein said composition of matter is shaped so that there is provided within said composition of matter one or more apertures, the combination thereof with one or more flexible resilient restraining members which restrict the movement of detonating fuse material or blasting cap material'disposed within said aperture, at least a part of said restraining member or members being embedded in the body of said composition of matter, the remainder of said member or members being disposed within said aperture in a flexi ble resilient condition.

2. A device according to claim 1 wherein the said flexible restraining member is a flexible sleeve.

3. A device according to claim 1 wherein the said flexible restraining member is in the form of an annulus the larger circumference of which encompasses said aperture and the smaller circumference of which lies within said aperture.

4. A device according to claim 1 wherein the said flexible restraining member comprises material selected from the group consisting of natural rubber and synthetic rubber.

5. A device according to claim I wherein the said flexible restraining member comprises a foamed plastic composition.

6. A device according to claim 5 wherein said plastic composition is a polyurethane composition. 

1. IN A KNOWN DEVICE COMPRISING A SENSITIVE SECONDARY HIGH EXPLOSIVE COMPOSITION OF MATTER CAPABLE OF REINFORCING A DETONATION WAVE FROM A PRIMARY EXPLOSIVE OR DETONATING MEANS AND COMMONLY REFERRED TO AS A BOOSTER, AND WHEREIN SAID COMPOSITION OF MATTER IS SHAPED SO THAT THERE IS PROVIDED WITHIN SAID COMPOSITION OF MATTER ONE OR MORE APERTURES, THE COMBINATION THEREOF WITH ONE OR MORE FLEXIBLE RESILIENT RESTRAINING MEMBERS WHICH RESTRICT THE MOVEMENT OF DETONATING FUSE MATERIAL OR BLASTING CAP MATERIAL DISPOSED WITHIN SAID APERTURE, AT LEAST A PART OF SAID RESTRAINING MEMBER OR MEMBERS BEING EMBEDDED IN THE BODY OF SAID COMPOSITION OF MATTER, THE REMAINDER OF SAID MEMBER OR MEMBERS BEING DISPOSED WITHIN SAID APERTURE IN A FLEXIBLE RESILIENT CONDITION.
 2. A device according to claim 1 wherein the said flexible restraining member is a flexible sleeve.
 3. A device according to claim 1 wherein the said flexible restraining member is in the form of an annulus the larger circumference of which encompasses said aperture and the smaller circumference of which lies within said aperture.
 4. A device according to claim 1 wherein the said flexible restraining member comprises material selected from the group consisting of natural rubber and synthetic rubber.
 5. A device according to claim 1 wherein the said flexible restraining member comprises a foamed plastic composition.
 6. A device according to claim 5 wherein said plastic composition is a polyurethane composition. 